Though some had hoped for action on Wednesday, the regional authority overseeing the $6 billion rail-to-Dulles project will not discuss - or possibly vote on - a labor provision that is threatening to derail the second leg of the 23-mile rail line until as late as June 6.

The board of directors for the Metropolitan Washington Airports Authority (MWAA) had already voted to grant a 10 percent scoring bonus to contractors that pledge to use a union-friendly labor agreement on Phase 2 of the $6 billion Dulles Metrorail project. However, Virginia Transportation Secretary Sean T. Connaughton has said the commonwealth will not contribute the $150 million it has pledged for the second leg of the project if the agreement isn’t dropped.

“We’re either going to reaffirm our current position or restate a new position,” said board Chairman Michael Curto. “We’re going to have a full, frank, open discussion in public.”

Three of the 13 board members were absent from Wednesday’s meeting, and MWAA President and CEO John “Jack” Potter cited an amendment in the still-pending Virginia state budget dealing with union preferences. By waiting, he said, the board could preclude any arguments that it was violating Virginia law.

Proponents of the measure point to the fact that Dulles Transit Partners, the lead contractor for Phase 1 of the 23-mile project, voluntarily adopted the pre-project agreement outlining the terms and conditions of work, which proponents sayprovided a steady, reliable supply of union labor and kept costs down. But opponents say this type of agreement discriminates against the 96 percent of Virginia construction workers who are non-union, and could drive up costs by scaring off potential bidders wary of adopting it.

Mr. Potter said the so-called “project labor agreement” (PLA) is a huge sticking point for Loudoun County, which has until July 4 to decide whether to remain a funding partner on Phase 2 of the project - currently projected to extend from Wiehle Avenue in Reston through Washington Dulles International Airport and into Loudoun. Metro, MWAA, Fairfax County, Virginia and the federal government are the other partners in the 23-mile project.

Loudoun is slated to provide 4.8 percent of the project funds. If Loudoun should opt out of the deal, though, it would not be a simple matter of shifting funds around; the already signed contracts and agreements would be thrown into flux, likely delaying the project further.

“Loudoun has been very public that if the PLA is still in the project, they’re going to vote against the project,” Mr. Potter said.

The issue prompted a tense exchange between board vice chairman Thomas M. Davis III, a former congressman from Northern Virginia, and Robert C. Brown, an MWAA board member, at Wednesday’s board meeting.

Mr. Brown accused Virginia of threatening to renege on its pledged share of funds for the project if its conditions were not met. He wanted the board to officially reaffirm the agreement it signed with the state.

“The fact is, not only did Virginia inexplicably change its mind,” he said, “but Virginia and its most senior official continue to repeat that this authority is not complying with Virginia law. We need to say it loudly and clearly.”

Gov. Bob McDonnell, while saying repeatedly that he is committed to the project, has been fighting the authority over the labor agreement, as well as supporting a federal law increasing the number of Virginia’s seats on the board.

Mr. McDonnell inserted language into the two-year budget ending June 30 that some legislators interpreted as withholding any further state money for the project until Virginia’s representation on the 13-member MWAA board was increased, as required by a federal law introduced by U.S. Rep. Frank R. Wolf, Virginia Republican. But the General Assembly rejected Mr. McDonnell’s amendment, and according to legal opinions, it is not currently enforceable.

Nonetheless, Mr. Davis likened Mr. Brown’s proposal to a stunt, and moved to defer the resolution to the board’s next meeting.

“This is obviously an attempt to embarrass the governor,” Mr. Davis said. “I don’t think it’s what I would call a mature, professional way to handle this. I don’t think this helps with Loudoun or anything else.”

Mr. Davis said outside the meeting room that the project doesn’t need the $150 million pledged by Virginia today, but if the board issued its request for qualifications for contractors in its current form, “we would probably see the $150 million evaporate.”

“My concern all along has been, we want Loudoun in, and we want the state money,” he said. “Now we’re going to take steps to get at it.”